Lidar stands for LIght
Detection and Ranging and is very similar to the better known Radar.
Basically, a laser pulse is sent out of a transmitter and the light particles
(photons) are scattered back to the receiver. The photons that come
back to the receiver are collected with a telescope and counted as a function
of time. Using the speed of light (~3X108 m/s) we can
then calculate how far the photons have traveled round trip. Photons
can be scattered back off of many different things, such as other particles
(aerosols or molecules) in the atmosphere or your car (police laser radar)
for instance. There are also many different ways to use the signal
that is collected by the telescope. Some of these uses include; catching
speeders, detecting aerosols (pollution, dust, etc.) in the atmosphere,
detecting water vapor content in the atmosphere, measuring winds, as well
as many other applications. The diagram below shows the basic
concept of a lidar that uses particles in the air to scatter the out going
photons back to the receiver. The background for this page, and many
of our other ARSL pages, is actual lidar data showing the marine boundary
layer with a dust plume above it. A great source for more specific
information on lidar systems can be found through links on the
Lidar
Researcher's Home Page.